Process for the purification of tobacco smoke



United States Patent 3,288,151 PROCESS FOR THE PURIFICATION OF TOBACCOSMOKE Oliver W. Burke, In, 506 Intracoastal Drive, Fort Lauderdale, Fla,and Eldon E. Stahly, Pompano Beach, Fla; said Stahly assignor to saidBurke No Drawing. Original application Aug. 13, 1963, Ser. No. 301,879.Divided and this application Aug. 7, 1964, Ser. No. 398,465

1 Claim. (Cl. 131262) The present application is a division ofapplication Serial No. 301,879, filed August 13, 1963, and has beenfiled pursuant to a requirement for restriction made in said applicationSerial No. 301,879 under 35 U.S.C. 121.

This invention relates to the improvement of tobacco smoke, filters, andcigarettes for the reduction of metal content, e.g., metal carbonyls, inthe smoke. Strictly speaking, a metal carbonyl is a compound of metaland carbon monoxide, but in a broader sense the term metal carbonyl alsoincludes the analogous metal nitrosyl carbonyls and the metalhydrocarbonyls, which are similar compounds in which one of the carbonylgroups has been replaced by a nitrosyl or a hydrocarbonyl group, andexcept where the context indicates to the contrary, the term is employedin said broader sense herein. Metals may also be present in the smoke inother forms, and the term metal content of the smoke has reference tothe metal present therein Whether in the form of gaseous metal carbonylcompounds or otherwise.

Objects of the invention, severally and interdependently, are to providean improved cigarette having a substantially reduced content of metal inits smoke output as compared to conventional plain or filter-tippedcigarettes; to provide a process for the purification of tobacco smokeby removing metals therefrom by converting the same to non-volatilematerials; to provide an improved cigarette smoke from which selectedmetals are substantially reduced or eliminated; to provide an improvedmethod and cigarette, or cigarette filter, in which metals present intobacco smoke in small amounts are converted to forms, e.g.,non-volatile materials, in a manner which effectively prevents theirleaving a cigarette in the smoke; and to provide an improved method andcigarette in which a ligand material is reacted with'metals in thetobacco smoke and converts them into non-volatile compounds.

Other objects and advantages of the invention, and of preferredembodiments thereof, will be apparent from the following description andfrom the illustrative examples appended thereto.

The invention resides in the new and useful methods and products hereindisclosed, and is more particularly defined in the appended claim.

GENERAL DESCRIPTION Conventional tobacco smoke, more particularlyconventional cigarette smoke, contains substantial traces of metals, andespecially of transition metals, e.g., nickel, cobalt and iron, and suchmaterials are reported to be toxic and carcinogenic to animals.

Thus, it has been reported in a paper by the Drs. F. W. Sunderman (Sr.and Jr.), based on tests of six different brands of cigarettes, thatnickel carbonyl containing from 0.4 to 0.6 microgram nickel percigarette (corresponding to about 20% of the total nickel of thetobacco) passes through the butt and filter of conventional plain orfilter cigarettes, reaching the smoker (Medical Science, page 617, May25, 1961; American Journal of Clinical Pathology, 35, 203 (1961)). Instudies with rats, small amounts of nickel carbonyl were found by theDrs. Sunderman to be carcinogenic. The nickel delivered in the smokedrawn from the butt ends of the cigarettes amounted to up to 8micrograms nickel per pack of 20, or 23.5 micrograms nickel as nickelcarbonyl per pack of 20 of unfiltered cigarettes; and up to 12micrograms nickel or 35 micrograms of nickel as nickel carbonyl per packof filtered cigarettes. On the basis of their studies cumulativeexposure to these quantities of nickel was suggested by the Drs.Sunderman to be a possible cause of the so-called smokers pulmonarycancer. Based on the reported figures, a person who smokes a pack ofcigarettes per day over a period of a year subjects himself to about oneand one-half times the amount of nickel required to induce pulmonarycancer in rats, which are considered to be notably resistant topulmonary cancer.

Aside from the nickel reported, it has been found that traces ofvolatile cobalt and iron are also present, apparently as carbonyls, incigarette smoke. is present in somewhat smaller amounts than the nickel,about 1.3 micrograms of cobalt passing the filters per pack of filtercigarettes; and the iron is present in at least about twice the amountof nickel in the smoke of some brands of cigarettes.

Aside from the carcinogenic aspects of metal carbonyls reported by theDrs. Sundermanfit has long been known that such metals are highly toxicand dangerous materials even in trace amounts. Thus Sax, Handbook ofDangerous Materials, published in 1951 by Reinhold Publishing Company,New York, prescribed a maximum allowable concentration of cobalt in theair as 0.4 part per million, and the Twenty-Second American Conferenceof Government Hygienists in April 1960 placed the maximal atmosphericconcentration of nickel carbonyl for a working day at 1 part per billion(AMA. Arch. Environmental Health 1, 144, year 1960). Iron carbonyl isalso considered to be toxic, although less toxic than nickel and cobaltcarbonyls. Accordingly, the cumulative toxicity effects of these threemetals in tobacco smoke can be expected to be greater than that reportedfor nickel alone.

Likewise, aforesaid Drs. Sunderman in the above cited paper,demonstrated that cigars and pipe tobacco contain nickel in amountssimilar to cigarette tobaccos, and similar amounts of nickel per gram oftobacco smoked can reach the smoker. Some pipe tobaccos contain 6micrograms nickel per gram of tobacco, 6 micrograms cobalt per gram oftobacco and over 400 micrograms iron per gram of tobacco, of which overa microgram of each metal per gram of tobacco smoked can reach thesmoker in conventional methods of smoking.

Hence it is evident that the quantities of transition metal present inthe smoke from conventional plain and filter cigarettes and from cigarsand pipe tobacco exceed the quantities deemed objectionable by the aboveauthorities.

By the present invention such content of transition metal may be reducedin, or practically eliminated from, the tobacco smoke from such smokingarticles, and this invention thus can serve as a safeguard to smokersagainst excessive exposure to such metals.

The cobalt The new process for the treatment of tobacco smoke is basedon the reduction of transition metal content of tobacco smoke by theformation of non-volatile complexes or low-volatility complexes or saltsby combination of the metal carbonyl or other metal content of thetobacco smoke with a ligand, which for the purposes of this inventionsaid ligand is an aromatic compound having a combination of at least onehydroxy radical and at least one other polar radical attached to thesame aromatic nucleus, which compound acts as a complexing agent to formcomplexes of low volatility with transition metal content of tobaccosmoke in the presence of other constituents of tobacco smoke, moreparticularly in the presence of moist carbon dioxide. The practice ofthe invention does not depend on the formation of exact empiricalcomplexes since mixtures of such complexes may be formed with equalbenefit for the process. Thus the ligands of this invention areprincipally aromatic compounds having one or more hydroxy (oxy) radicalsattached to aromatic nuclei and such hydroxy groups in most of theseligands are in the ortho position to certain other groups which, withsaid hydroxy group of said compounds capable of forming relativelystable salts or complexes, or chelates of certain transition metalcompounds, e.g., the carbonyls of nickel cobalt and iron.

Ligands hereof containing transition metal chelating groups andincluding therearnong at least one hydroxy group can be represented bythe following Formula A:

TABLE A Markush Group of Radicals from which the Radical (x) in theFormula A is selected Ligand Group Comprising both radical (x) and thehydroxy radical ortho thereto 1. Carbonyl [:0]

2. Carboxyl [0:0]

o-Hydroxy-carbonyl.

o-Hydroxy-amide.

o-Hydroxy-N-mono-substituted amides.

o-Hydroxy-N-disubstituted amides.

o-Hydroxy-azomethine.

o-Hydroxy-azo.

o-Hydroxy-nitroso.

O 9. Lactone [O=C 10. Hydroxy [-OH] Hydroxyl-lactone.

o-Hydroxy-hydroxy.

When the ligands hereof have chromophore and/or auxochromophore groupsthey are colored, for example, the mordant type dyes have metalcomplexing groups similar to those set forth in Table A above andtherefore such mordant dyes in their unmordanted form may be employed asligands for the purposes of this invention and the members of themordant class of dyes are set forth throughout pages 1405-1616 of volume1 (second edition 1956) of the Colour Index (edited by The Society ofDyers and Colourists, and The American Association of Textile Chemistsand Colorists).

Iron, nickel and cobalt or other transition metal compounds present intobacco smoke will combine with unmordanted mordant dyes in the presenceof other ingredients of tobacco smoke.

Thus mordant dyes in their unmetalized form (unmordanted form) which arerelatively non-toxic and capable of complexing or combining with thetransition metals of tobacco smoke are considered ligands for thepurposes of this invention.

This invention comprises:

(1) the method of treating tobacco smoke which comprises reducing thecontent of transition metal therein by contacting said smoke with aligand as herein described;

(2) a filter element for reducing the transition metal content oftobacco smoke, said filter element including a substance comprising aligand as herein described;

(3) a new article of manufacture, a cigarette having exposed in the pathof the tobacco smoke therein means for reducing the content oftransition metal thereof, said means comprising a ligand; and in thisinvention the term ligand means a substance which contains at least twofunctional groups which are attached to two adjacent carbons of anaromatic moiety and one of said functional groups comprising a hydroxygroup and the other of said functional groups being a group having atomsselected from the class consisting of oxygen, nitrogen and combinationsof these atoms and said other group being selected from the classconsisting of carbonyl, carboxyl, amide including N-mono-substituted andN-disubstituted amides, azomethine, azo, nitroso, oxazone, oxazine,lactone, oxy and combinations of such groups and said ligand beingcapable of removing transition metal compounds from tobacco smoke.

Thus volatile metal compounds in the cigarette smoke by the presentinvention are converted to non-volatile complexes by contacting thesmoke with one or more ligand aromatic ortho-hydroxy compounds as abovedefined.

The complexes are formed by passing the smoke containing the metalcompounds into contact with one or more of said ligands or over orthrough a filter material acting as a carrier body for the ligandmaterial, and preferably comprising fibrous material, for example,cellulose ester tow, e.g., cellulose acetate tow prepared with theligand thereon and/or therein, or wholly or partly coated with theligand or with material such as activated carbon carrying the same.

To remove the transition metal compounds at least in part from tobaccosmoke the ligands hereof are interposed in the path of said tobaccosmoke as for example by depositing 0.01 to 10% preferably 0.5 to 5% byweight of such ligand material on the filter or other material locatedin the path of the tobacco smoke.

In the practice of the invention for example in making tobacco smokefilters one or more of the ligands or complex-forming compounds orcomponents with or without a solvent or plasticizer are preferablydispersed on solid adsorbents; for example, the liquid orcomplex-forming components may be vaporized onto an adsorbent material,or a solution of a ligand may be applied to adsorbent material such ascarbon, e.g., activated carbon, silica, pumice, vermiculite, clay,asbestos, polyesters, polystyrene, and cellulosic materials, e.g.cotton, cellulose, cellulose acetate, cellulose acetate-butyrate,cellulose propionate, tobacco, and other absorbing materials having ahigh surface area per unit weight or per unit volume.

The ligand material of the present invention may be incorporated in orwith the smoke-permeable bases, carn'ers or filters which themselves mayembody various adhesives, adsorbents and surface area augmentingmaterials, and such incorporation of ligand material also may be madeduring the manufacture of the filter material or filters and thus suchligand materials can be incorporated with the materials and during theprocesses as disclosed, for example, in US. patents as follows:

The invention as above disclosed will be more fully understood byreference to the following examples of materials which may be employedas ligands for the practice of this invention and which examples are tobe taken as illustrative and not restrictive of the invention.

1. The o-hydroxy-carbonyl ligand.-The ligands of this group embrace thestructure,

and include the following sub groups of ligands:

1(a). The aromatic hydroxyl-ketane ligands.This group ofo-hydroxy-carbonyl ligands having the formula Number in which R R and Rare radicals selected from the group consisting of hydrogen, C to Chydrocarbon radicals (including alkyl, aryl, alkaryl, aralkyl,cycloalkyl, alkylcycloalkyl radicals), =CO, CHO, -COOH, OH, OR, NONHCOR, SO NH SO NHR, -SO NRR, SO R, SO H, CONH2, CONHR, CONRR, NH NHR,.NRR and halogen radicals; and R is a C to C hydrocarbon radical.

Usable as ligands of thisgroup are compounds heretofore used as mordantdyes as for example those represented by Formulas I and II hereafter andthe like as follows:

(I) HO OH HO- gf-CH:

Alizarine Yellow C (Cl, No. 57000) (II) HO OH Alizarine Yellow A (Cl,No. 57005) The O1. numbers as used herein refer to compounds heretoforeemployed as dyes or dye intermediates and such C.I. numbers in the abovecited Colour Index 2nd Edition (1957). Where, in the Colour Index, theCl.

6 number cited refers to a metalated dye, e.g., with copper, chromium,cobalt, nickel or iron, it is to be understood that as a ligand hereofthe compound should be in unmetalated form in reference to these metals.

1 (b). The naphthaquinone ligands.The o-hydroxycarbonyl ligands of thisgroup have one of the formulae wherein R and R are radicals selectedfrom the group consisting of NHC H OC H OH, SO H and hydrogen radicals.

Usable as ligands of this group are compounds heretofore employed asnaphthaquinone dyes and designated by the Cl. numbers: 57010, 57015,57020, 57025 and 57030.

1(0). The anthraquinone ligands.This group of ohydroxy-carbonyl ligandshave the formula *Including the isomer with .N in starred position,

wherein R and R are selected from the radicals consisting of OH, -SO H,NO COOH, NH and hydrogen.

Usable as ligands of this group are compounds heretofore employed asanthraquinone dyes and designated by the Cl. numbers:

and the like.

1(d). The anthrahydroxy phthalein ligands.--This group ofo-hydroXy-carbonyl ligands is represented by compounds heretoforeemployed as anthrahydroxyphthalein dyes and designated by the Cl.numbers 45505 and 45510, and the like.

2. The hydroxycarboxyl ligands.--The ligands of this group embrace thestructure and include the following subgroups of ligands.

2(a). The substituted phenyl-o-hydroxycarbonyl ligands.Represented bythe formula wherein R R and R are similar radicals to those set forthunder 1(a) heretofore.

7 2(b). The substituted naphthyl-o-hydroxycarbonyl ligands.Representedby the formula wherein R R and R are similar radicals to those set forthunder 1(a) heretofore.

Examples of these o-hydroxycarbo-xyl ligands include:

2(0). The azo-O-hydroxycarboxyl ligands-The ligands of this groupinclude the monoazo, disazo and trisazo compounds Witrhthe lowermolecular weight compounds usually being preferred for such can bind agreater quantity of metal based on the weight of the compound. Thesecompounds, if desired, may be applied to the filter material as a sodiumsalt, as for example:

COONa.

'C.I, Mordant Yellow 18 (-0.1, No. 13990) and may then be acidified atleast in .part to yield the free o-hydroxycarboxylic acid CODE 2(c-1).The m onoazo o-hydroxycarboxy ligands include ligands represented by theformulae:

RL M laH wherein R R and R are similar radicals to those set forth under1(a) heretofore.

8 Usable as ligands of this group are compounds heretofore used as dyesand designated by the Cl. Nos.:

2(c2). The disazo-o-hydroxy-carboxyl ligands.Tlhe ligands of this groupare similar in structure to the monoazo compounds set forth under 2(c-1)heretofore except such are d-isazo compounds having two azo groups andbecause of their higher molecular Weight are less preferred.

2(c-3). The trisazo and polyazo-o-hydroxy-carboxyl ligands.--'Ilheligands in this group are similar in structure to the monoazo compoundsset forth under 2(c1) 'heretofone except that these compounds have threeazo groups and therefore because of their higher molecular weight areless preferred.

2(d). The triarylmethane-o-hydroxy-carboxyl ligands.-Ligauds of thisgroup include the triphenyl-metihane o-hydroxy-carboxyl ligands such asthe compounds heretofore used as dyes designated by the Cl. numbers:

The compounds lheretofore used in the p'hth'alein dyes designated by C1.numbers 45445, 45450 and 45455 may also be employed as ligands in thepresent invention.

3. The o-hydroxy-amide ligands.This class comprises the ligandsrepresented by one of the formulae:

in which R and R are radicals selected from the C to C hydrocarbonradicals. More succinctly, these ligand compounds are the orthohydroxyaromatic amides in which the amide group has the formula -CONR R whereinR and R are radicals selected from the group consisting of hydrogen andthe C to C hydrocarbon radicals.

4. The o-hydroxy-azomethine ligands.This group of o-hyd-roxy-azo-methineligands have the common radical represented by the formula in which R isa hydrocarbon or substituted hydrocarbon radical and include ligandsrepresented by the following formula including the hydroxy-oximes,hydroxy-aldirnines, hydroxy-ketimines and such compounds as thefollowing wherein R and R are similar radicals to those set forth under1(a) heretofore.

5. The o-hydroxy-azo ligands.The o-hydroXy-azo ligand can embrace thestructure C-OH and include the following subgroups of ligands:

(a-1). Monoazo and disazo ligand compounds.- Having the o-hydroxy-azogroup including such structures as represented by the following:

and similar dis-azo compounds in which R and R are radicals selectedfrom the radicals set forth under 1(a), e.g. CI-I NO Cl, SO H, COOH, NHCONH or hydrogen radical etc.

5(1)). The 0,0-dihydroxy-azro ligands.These ligands embrace thestructure and include compounds heretofore employed as monoazo, disazoand polyazo dyes. They have the structural formulae:

wherein R R and R are similar radicals to those set forth under 1(a)heretofore.

Examples of the ligands of this group are the o,o-dihydroxy-azo ligandcompounds, which compounds have heretofore been employed as dyesdesignated by the Cl. numbers:

10 Among the above examples of [ligands are also included dihydroXy-azoligands which have a nitrogen containing ring, e.g., a pyrazole ring ora quinoline ring such as the following:

and the like.

6. The o-hydroxy-nitroso ligands-Ligands having the o-hydr-oxy-nitrosogroup embraced by the following structures and -C=NOH CN=O includecompounds such as:

1nitroso2-naphthol-6-sulfonic acid 1nitroso-Z-naphthol-4-sulfonic acidl-nitroso-Z-naphthol 2-nitroso-1-naphthol Chromotropic acid dioximeNitnosochromotnopic acid 2,4-dinitroso-3,5-dihydroxy-toluene2,4-dinitroso-1,3dihydroXybenzene o-NitrosocresolZ-nitroso-1-naphthol-4-sulfonic acid 4-nitrosoresorcino1 Nitroso-R-saltp-Nitroso-thymol 7. The o-hydroxy-oxazo'ne ligands.Ligands having theortho-hydnoxy-oxazone group are exemplified lby compounds heretoforeused as dyes and designated by the Cl. numbers 51405, 51410.

8. The o-hydroxy-oxazine ligands.Ligands having theort'ho-hydroxymxazine group 1 1 include compounds heretofore used indyes and identified by the Cl. numbers 51025, 51030, 51040, 51045,51050, 51060, 51065 and 51070.

9. The hydroxy-lactone ligands.-Ligands of this class have both thehydroxy group and a lactone group and as such ligands may be employedcompounds heretofore used as dyes and identified by the Cl. numbers55000, 55005 and 55010.

Among the compounds included in subclasses 1 through 9 above are themordant dyes and for the purposes of the present invention the mordantdyes are incorporated in the cigarette filters in essentiallyunmordanted form, and thus are present in a form capable of combiningwith and extracting from tobacco smoke the transition metal contentthereof.

By the term unmordanted is meant the mordant dyestuff is essentiallyfree of metal ions which mordant or insolubilize the dyestuff, e.'g., isessentially tree of aluminum, iron, manganese, chromium, nickel, cobalt,copper, zinc, calcium, lead and other metals including the transitionmetals of sub-groups 1V, V and VI of the Periodic Table. For purposeshereof the mordant dyestuff is sometimes employed in the form. of awater soluble salt, e.g., an alkali metal, ammonia or amine salt.

10. The o-dihydroxy ligands.-The ligands of this group have at least onearomatic radical with two bydroxy groups in ortho position to oneanother and such ligands embrace the following structure:

Included among the compounds of this class is pyrolgallol, catechol andthe alkyl substituted catechols, pyrocatechol, methyl pyrocatechol, the1,2,3-trihydroxybenzene, the 1,2,4-trihydroxy benzene, thetetrahydroxyabenzenes, hexahydroxy-benzene, similar compounds of thenaphthalene series gallic acid, m-digallic acid, the tannic acids, thertannins protocatechuic acid, 1,2-dihydroxybenzene-3,5- disulfonic acid,9-methyl-2,3,7-trihydroxy-6-fiurone, and the dyestuffs having suchstructure as for example pyroca-techol vi'olet EXAMPLES In the followingexamples wherein coating procedures are not otherwise described, filterswere prepared as follows: The manufacturers filters were removed fromBrand A filter cigarettes and 0.5 ml. of an aqueous and/ or alcoholicsolution of the ligand was added dropwise to the filters. The individualfilters average 0.125 g. in weight. The proportions of water and alcoholin the solution were adjusted for ligand solubility considerations.Where the ligand was a dyestufi and the acid form of the dye was desiredthe major portion of the solvent mixture used was alcohol, and therequired amount of hydrochloric acid was added thereto to convert thecommercial sodium or ammonium salt of the dye to its acid form. Theinorganic salts present in most commercial dyes were removed bydissolving the dye in a solvent e.g., alcohol and filtering or theinsoluble salts were allowed to settle out and only the soluble organicdye material was added to the cigarette filters. When the salt of thedye was desired as the coating agent the alcohol was diluted with water,thus increasing the dye salt solubility. The amount of dye present inthe 0.5 ml. of solution was varied to give from 1% to 10% as desired.The filters were observed to be substantially uniformly colored by the0.5 ml. of dye solution, and were dried at 50 C., atmospheric moistureequiliibrated at room temperature and about 70% humidity, and eachfilter was employed for filtering the smoke of one Brand A cigarettefrom which the manufacturers filters had been removed. A sample foranalysis consisted of 60 smoked filters.

An alternate procedure was to use the dyed filter as a back-up filterfor smoking Brand A filter cigarettes. In this procedure a directcomparison of effectiveness of the transition metal absorptions byconventional filters and the filters of this invention is possible.

The analysis of the tobaccos of the Brands A, B, C and D employed inthese tests showed the following range of metal contents.

Since such variations occur in the metal content of the same brand ofcigarettes it is apparent that the smoke will vary widely in metalcontent and each lot of cigarettes must have control tests run withconventional filters for comparison with the ligand treated filters ofthis invention.

u 0.8 to

Example 1 A suspension-solution Was prepared by stirring 1 gram of thered compound 2,4-dibenzene-azoresorcinol, with a mixture of 60 g.benzene and 15 g. isopropanol. Cellulose acetate tow (5.024 g.) wasimmersed in the resultant suspension-solution for 18 hours and then,with 50 g. of absorbed liquid, was placed in a 70 C. air stream for 2hours. The tow was equilibrated With the atmospheric moisture until aconstant weight was reached and the coated tow contained 10% of the redcompound. The tow was divided into 20 portions weighing 0280:0005 g. andeach portion was employed as a back-up filter for smoking two Brand Afilter cigarettes. The back-up filter was prepared by fitting the towsnugly into a fi I.D. glass tube which served as a cigarette holder forthe cigarettes. The amounts of iron and cobalt absorbed per cigarettesmoked were as follows for the manufacturers filter and the back-upfilter:

Back-Up Filter (micrograms/ cigarette) Manufacturers Transition MetalsFilter (micrograms/ cigarette) 15. 0 None Iron Cobalt Example 2 '13 thethirty used back-up filters showed absorption of 38.8 micrograms of ironper cigarette smoked while the manufacturers filter showed absorption of2 micrograms of iron per cigarette smoked. The structure of this dyematerial is as follows:

OH I r I OH;

Example 3 Five grams of C.I. Mordant Yellow 30 (C.I. 18710) wasdissolved in 400 grams warm water as in Example 1 and 7.734 g. ofcellulose acetate tow was immersed in the solution for 5 minutes,squeezed, immersed in acid, squeezed dry, and dried at 70 C. Theequilibrated sample contained 2.5% of the dye ligand material. SixtyBrand A filter cigarettes were smoked in pairs as in Example 2 using a0.258 :0.005 g. portion of the dyed tow as a back-up filter. Analysis ofthe used back-up filters showed absorption of 17.6 micrograms of iron,0.30 microgram of nickel and 0.43 microgram of cobalt per cigarettesmoked vs. 3.2, 0.17 and 0.18 micrograms of iron, nickel and cobaltabsorbed respectively by the manufacturers filter per cigarette smoked.The structure of the dye ligand mate-rial of this example is:

Example 2 was repeated using the dye C.I. Mordant Blue 1 (C.I. 43830)with 8.3 grams of tow. The wet material was immersed in dilutehydrochloric acid solution and dried. The coated tow was used as back-upin smoking sixty Brand A filter cigarettes which were smoked in pairsusing a 0.277 g. -0.005 g.) portion of the dyed tow as back-up filterfor each pair of cigarettes. Analysis of thirty used back-up filtersshowed absorption of 0.76 microgram of nickel per cigarette smoked vs.0.17 microgram nickel absorbed per cigarette for the manufacturersfilters.

The structure of this dye ligand material is:

COOH

or O Example Example 4 was repeated but omitting the acid treatment,thus allowing the C.I. Mordant Blue 1 ligand dye to remain as the sodiumsalt of the structure shown in Example 4 (the treated tow absorbed 4%dry). Smoking of 60 Brand A filter cigarettes in pairs was conductedusing a 0.262 g. (r0005 g.) portion of the tow as backup filter for eachpair of cigarettes. Analysis of the used back-up filters showedabsorption of 20.0 micrograms iron, 1.8 micrograms nickel and 0.43microgram of cobalt per cigarette smoked in comparison With 3.2, 0.17and 0.18 micrograms of iron, cobalt and nickel per cigaretterespectively absorbed by the manufacturers filter during smoking.

14 Example 6 The dye C.I. Mordant Red 3 (C.I. 58005) was used as thesodium salt in this experiment to coat 7.55 g. of cellulose acetate towto give 1.3% dry dye content. The smoking test was conducted as inExample 2. The back-up filters, of this invention showed absorption of77.5 micrograms iron, 0.61 microgram nickel and 0.235 microg-ram cobaltper cigarette smoked vs. 3.2, 0.17, and 0.18 microgram iron, nickel andcobalt respectively per cigarette for the smoked manufacturer's filter.The structure of this dye is as follows:

SO Na Example 7 1 COOH Example 8 PD & C Yellow No. 6 (C.I. 15985) wasused to coat cellulose acetate filters of Brand A filter cigarette. Theaqueous solution of the commercial dye (5 g. in 400 ml. water) coatedthe tow with the sodium salt and the wet tow was immersed in 1%hydrochloric acid solution to convert it to the free acid form:

s o H The final dried and equilibrated tow showed about 1.3% dye hadbeen absorbed. Each filter was used to filter the smoke of a Brand Acigarette. Likewise 300 non-dyed filters were used as a control insubstantially identical smoking tests. Analyses of sixty ligand treatedfilters showed the following absorptions of iron and nickel percigarette smoked in comparison with the manufacturers filters:

Non-dyed Manu- Dyed Manu- Transition Metal f acturers Filters faeturersFilters (micrograms/cigarette) (micrograms/cigarette) Iron 1. 0 3. 7Nickel 0. 16 0. 27

Example 9 Chrome Fast Black FWX or C.I. Mordant Black 5 (C.I. No. 26695)was employed as in Example 8 to dye filters taken from Brand A filtercigarettes. About 8% of total dye material was found absorbed by thedried dyed tow. The smoking test conducted as in Example 8 showed thefollowing metal absorptions in comparison with the controls:

Example 8 was repeated but using Chrome Fast Brown EBC or Mordant Brown1 (CI. No. 20110) as the dye to treat the cellulose acetate tow and thedye salt was not acidified. The dyed filter contained about 3.5% totaldye components. Comparative data of metal absorption from the smokeusing the non-dyed and dyed filters were as follows:

Non-dyed Manu- Dyed Manu- Transition Metal facturers Filters facturersFilters (micrograms/cigarette) (micrograms/cigarette) Iron None 71. 8 0.01 0.20 Cobalt None 0. 09

The structure of the dye used in this example is as follows:

O 2N HzN N Hz S O 3N3.

Example 1 1 This example is similar to Example 8 except that SuperchromeBrilliant Violet NR or Cl. Mordant Violet 1 (Cl. No. 43565) was employedwithout acidification. The filters contained 8.5% dye material. In anidentical smoking test as used in Example 8 the following absorptions ofmetals were obtained:

This example was made similar to Example 7 but Tartrazine (FD & C YellowNo. was used without acidification as the dye material. About 2% dyematerials were absorbed by the filter i-n dyeing. Analyses of filtersafter smoking showed the following data:

Non-dyed Manu- Dyed Manu- Transition Metal faeturers Filter faeturersFilter (micrograms/cigarette) (micrograms/cigarette) Iron 1.0 3. 0Nickel 0. 16 0. 35 Cobalt 0. 0 0. 016

The structure of the dye of this example was:

HO ma NaO S-C 'N=NG N l C O O Na Acidification of the dye ligandimproves the ability of the filter for absorption of metals from thesmoke.

Example 13 The cellulose acetate tow (7.540 g.) was coated with 8.5%salicylic acid from a mixture of 5 g. salicylic acid, 112.5 g.isopropanol and 225 g. water. The coated tow was divided into thirtyportions each weighing 0.269 10.005 g., and each portion was used .asfilter to smoke two Brand C cigarettes. Likewise a control smoking testwith an equivalent amount of uncoated tow as filter material was smokedfor comparison. Analyses of the filters from these two tests showabsorption in micrograms of metals absorbed from the smoke per cigaretteas follows:

Uneoated Tow Ligand Coated Tow Transition Metal (micrograms/cigarette)(micrograms/cigarette) Example 14 In this example the ligand materialwas gallic acid. Gallic acid coated cellulose acetate tow was preparedcontaining about 4.3% gallic acid. The coating solution consisted of 5g. gallic acid, 200 g. isopropanol and 50 g. water, the amount of towused was 17.295 g., drying time was 15 hours C. and atmospheric moistureequilibration time was 29 hours. Smoking tests were conducted with 30portions of the coated tow each portion Weighing 0.260 g. i- 0.005 g.;each portion was used as a filter for smoking two Brand D non-filtercigarettes. Similar smoking tests with uncoated tow were also carriedout. Analyses of the filters with and without ligand material aftersmoking were as follows:

Conventional Ligand Treated Transition Metal Cellulose Acetate CelluloseAcetate (micrograms/cigarette) (micrograms/cigarette) 12. 6 31. 0 None0. 34

Example 15 Sterile Red Cross Cotton was treated with a 5% tannic acidsolution in water to prepare a filter material containing 19.2% tannicacid. The volume of solution was 130 ml., the weight of cotton was20.450 45., the immersion time was five minutes, the wet weight wasgrams, the

ters from smoking sixty cigarettes were analyzed for iron, nickel andcobalt. The following micrograms of metals were found to have beenabsorbed per cigarette smoked.

Sixty filters were removed from Brand A filter cigarettes, and werecoated by adding to each filter 0.5 ml. of a filtered solution of 5 g.of PD & C Red No. 4 dye in a mixture of 100 ml. water, 100 ml.isopropanol and 1.5 ml. 37% hydrochloric acid. After drying andequilibrating the filters were found to contain about 12% dye. Thestructure may be represented by the following formula:

Sixty Brand A cigarettes without the manufacturers filters were smokedusing as filter one of the above coated filters. After use in smoking,the filters were combined and analyzed for iron. The results showed that17.25 micrograms of iron had been absorbed per cigarette smoked. In anidentical smoking test using the manufacturers filters only 8.6micrograms of iron were absorbed per cigarette smoked.

Example 17 A solution of ligand material was prepared by dissolving 5 g.Alizarin Red S (C.I. 58005) in a mixture of 200 ml. isopropanol and 50ml. water containing 0.56 g. of hydrogen chloride, and filtering toremove inorganic salts. Sixty filters were removed from Brand Bcigarettes and were impregnated with the filtered Alizarin solution byadding 0.5 ml. of said solution to each of the sixty filters. The driedand equilibrated filters were found to contain about 6% of the ligandmaterial represented by the following formula:

OH I] I This is the acid form of the ligand material of Example 6.

Sixty of'the Brand B cigarettes, from which manufacturers filters hadbeen removed, were smoked using one of the coated filters above preparedfor each cigarette. The combined filters after smoking were analyzed fornickel and were found to have absorbed 0.64 micrograms of nickel percigarette smoked. Simultaneously a control smoking testwas made with 60Brand B cigarettes with the manufacturers filters. The combinedmanufacturers filters after use showed absorption of 0.0 microgram ofnickel from the smoke, thus demonstrating the effectiveness of theligand material.

Example 18 Sixty Brand A cigarettes were smoked as in Example 16 usingone of these above coated filters in place of the manufacturers filters.The filters were found by analysis to have absorbed 28.9 micrograms ofiron per cigarette smoked. This is to be compared with 8.6 micrograms ofiron absorbed per cigarette by the manufacturers filter.

HO S S0 11 Example 19 Sixty filters were removed from Brand A cigarettesand were coated by adding to each filter 0.5 ml. of a filtered solutionmade up by dispersing 5 g. of National Superchrome Garnet Y (0.1. 14290)in a mixture of 105 ml. isopropanol, 100 ml. water and 0.55 g. hydrogenchloride. The dried equilibrated filters contained about 9.7% of the dyeof the following structure:

OH HO In a smoking test as in Example 16 with sixty Brand A cigarettes(with manufacturers filters removed) the filters absorbed 0.4 microgramnickel per cigarette smoked vs. none for the control.

Example 20 Five grams of polygalacturonic acid was dissolved in 400 g.water at C. and 7.507 g. of cellulose acetate tow was immersed thereinfor ten minutes. The dried coated tow after equilibration with themoisture in the laboratory air showed a 13.5% content of the polygalacturonic acid. The coated tow was divided into thirty portions, eachweighing 0.289i0.005 g. and each portion was used to filter the smoke oftwo Brand D non-filter cigarettes. The combined filters after smokingshowed absorption of 9.2 micrograms of iron per cigarette smoked. In acontrol test 300 Brand D cigarettes were smoked using cellulose acetatetow filters made by the manufacturer of Brand D cigarettes and thesecommercial filters, in the absence of the ligand, removed only 2micrograms of iron per cigarette.

The effectiveness of the ligands hereof in removing trace metals fromtobacco smoke can be improved in most instances when such ligands arecombined with a suitable plasticizer. By the term suitable plasticizeris meant a plasticizer in which the ligand is soluble or at leastpartially soluble. v

The plasticizers for the ligands hereof may contain alcohol, ether,ester groups or combinations of such groups and examples of such includethe following: Triacetin (glyceryl triacetate), glycerine, glycerylmono-oleate, glyceryl mono-ricinoleate, Z-butoxyethanol, butoxyethyllaurate, diethylene glycol, diethylene glycol mono-ricinoleate, oliveoil, butyl oleate and for additional plasticizers see Table 15.3 (pages904-927) of The Technology of Solvents and Plasticizers by Arthur K.Doolittle, published 1954 by John Wiley & Sons, Inc., New York, NewYork.

While there have been described herein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that modifications and changes may be made withoutdeparting from the essence of the invention. It is therefore to beunderstood that the exemplary embodiments are illustrative and notrestrictive to the invention, the scope of which is defined in theappended claim, and that all modifications that come within the meaningand range of equivalency of the claim are intended to be includedtherein.

We claim:

a smoking article by the removal of volatile metal compounds therefrom,which comprises passing said smoke through a filter into the mouth ofthe user downstream therefrom, said filter comprising a ligand compoundwhich is an orthohydroxy aromatic amide other than a mordant dye, and inwhich the amide group has the formula CONR R wherein R and R areradicals selected from the group consisting of hydrogen and the C to Chydrocarbon radicals.

References Cited by the Examiner UNITED STATES PATENTS 2,815,760 12/1957Schreus et a1. 131-208 2,886,591 5/1959 Lautenschlager et a1.

OTHER REFERENCES Organic Sequestering Agents, by Chabarek and Martell,pub. 1959 by John Wiley, Inc., London, pp. 329-330.

SAMUEL KOREN, Primary Examiner.

MELVIN D. REIN, Examiner.

